Aluminum base alloy powder product



3,004,331 ALUMINUM BASE ALLOY POWDER PRODUCT Raymond J. Towner and John P. Lyle, Jr., New Kensington, Pa., assignors to Aluminum Company of America, Pittsburgh, Pa., a corporation of Pennsylvania No Drawing. Filed Nov. 8, 1960, Ser. No. 67,930 3 Claims. (Cl. 29182) g "is wrought powder products is not influenced to any significant extent by the oxide film which coats the atomized particles. 7

To achieve the desired level of strength at elevated temperatures, the alloy used to make the atomized particles should contain a minimum of 2.5% manganese and 2.5% copper. On the other hand, the maximum amount of manganese should be 12.5% and the maximum amount of copper should be 7.5% and the total should not be over since the worked article would have insufiicient ductility and might fracture under applied stresses at elevated temperatures. In any event, the manganese content of the alloy should exceedthat of the copper. To obtain the best results, from 4' to 10% manganese and from 2.5 to 7.5% copper should be employed. Manganese is substantially insoluble in The particles of'oxidedrstributed througnoufi ainnnnnm and the smalr proportion that maybe "dissolved has no significant efiect upon the properties of products made from the atomized particles. The presfiakes is time consuming andconseqnenflyiexpensivmnltngo encennthopper-gintheralloyidoesnotralterrthis. solubility has now been found, contrary to previous belief, that useful articles can be made from certain types of atomized aluminum alloy powders. As is well known, the atomization process involves disintegrating a stream of molten metal with a jet of gas, such as compressed air or by mechanical means. Very finely divided particles can be produced by this process that will pass through a standard Tyler 100 mesh screen. A

It is an object of this invention to provide articles having a high strength at elevated temperatures which are made from atomized particles of an aluminum base alloy containing manganese and copper as the principal added alloy components.

Another object is to provide such articles which do not depend upon the presence of oxide particles to impart strength at elevated temperatures.

Still another object is to provide such articles which do not require any preliminary thermal treatment to place them in condition 'for service at elevated temperatures. 7

.These and other objects are achieved by atomizing a substantially iron-free aluminum base alloy containing not less than 70% by weight of aluminum and from 2.5 to 12.5% by weight of manganese and from 2.5 to 7.5 by'weight of copper as theprincipal added alloy components, and subsequently consolidating and working a mass of such atomized particles under the influence of heat and pressure. The resultant articles have a density closely approximating that of the alloy if cast;.and in hot worked condition, they have a tensile strength of not less than 10,000 p.s.i. and a minimum yield strength of 9,000 p.s.i. at 600 F. after a 100-hour exposure. In comparison, a well-known wrought aluminumbase alloy nominally consisting of aluminum, 4.5% copper, 1.5% magnesium and 0.6% manganese, when solution heat treated and age hardened, has a tensile strength of 10,000 psi. and a yield strength of 7,500 psi. after an exposure of 100 hours at 600 F.

The aluminum-manganese-copper powder products can be readily worked under the usual hot working condi tions of temperature and pressure employed in fabricating conventional aluminum and aluminum base alloy articles. Furthermore, the hot worked product can be cold worked to a limited extent, if desired. No preliminary thermal treatment is required to develop the desired strength for service at elevated temperatures. The strength of the relationship to any appreciable degree. Copper, on the other hand, as is well known, is soluble in pure aluminum up to a maximum of approximately 5.5% at the eutectic temperature. However, the addition of manganese and other alloying elements of its group decreases the solubility of copper in the alloy to a low level. The small amount of copper which does dissolve in the aluminum alloy matrix serves to increase its strength, but the main strengthening etfect is produced by the small and finely dispersed alloy constituent particles. From a practical standpoint, therefore, it has not been found to be advantageous to thermally treat the, hot worked atomized powder product before placing it in service in order to increase the amount of copper held in the solution. ,The

rapid chill of the particles during the atomizationprocess serves to provide the sufiiciently finely divided constituent particles that are necessary for high strength.

The alloy may contain the usual impurities associated with aluminum, for example, silicon and iron.. Generally, the. silicon impurity should not exceed 0.8% and iron content should not be. more than about 1.0%. In

view of the relatively small amount of'iron impurity permitted in the alloy, composition is referred to herein as being substantially iron-free.

For some purposes, it may be desirable to add one or more elements selected from the group composed of nickel, cobalt, chromium, titanium, vanadium, zirconium,

tungsten, and molybdenum in amounts of 0.1 to 10% each, the total not exceeding 10% by weight. These elements act as hardeners and, like manganese, are substantially insoluble in the aluminum matrix.

The atomized alloy particles are preferably prepared by melting the alloy of the desired composition and projecting it through a suitably designed nozzle with the aid of compressed gas. The atomizing conditions should be so adjusted that none or only asmall proportion of the particles are larger than mesh microns opening) and that the majority of the particles will pass through a 200 mesh screen (74 microns opening). The particles produced in this manner are of an irregular shape, but are of substantially equiaxed dimensions and have an as-cast structure. The alloy constituents are very finely divided as a result of the drastic chill associated with the atomization process. The surfaces of the particles are, of course, oxidized if the atomization has occurred in air or in some other oxidizing atmosphere,

. sired temperature.

however, the oxide skin is very thin and the amount of oxide introduced into the final product is too small to have any significant effect upon the properties thereof.

To make wrought articles from the atomized powder, the powder may be initially formed into a compact that is subsequently worked or it may be charged directly to a compression chamber such as an extrusion press cylinder and be extruded therefrom after initial consolidation of a mass. The initial compact may be made by heating the powder to a temperature between 700 and 90091 and applying a sufficient pressure thereto for a long enough period of time to cause at least some consolidation and welding of the atomized particles. Pressures of 200 to 150,000 p.s.i. are satisfactory which are applied for varying periods of time from a minute or less to a few hours. 'Generally, a longer time is required where low pressures are employed. The compact may be left in the press cylinder and then extruded, or. it may be ejected, cooled, scalped', reheated to the hot working temperature and hot worked. In some cases it may be desirable to reheat the compact to temperatures as high as 1150 F. before hot working in order to obtain adequate workability. This should only be done if more than 3% manganese is present. -Where the powder is charged to a compression chamber, it may be initially heated to a temperature between 700 and 900 F. and then introduced to the chamber, or it may be charged cold and heated within the chamber to the de- After' an initial compression, the mass is then hot worked to the desired shape. Alternatively, it may be heated to an intermediate temperature, then charged to the chamber and brought to the desired temperature. When the powder is to be compacted and immediately extruded, it is generally convenient to compress the powdered mass against a blind die in a press cylinder and then substitute anextrusion die for. it to produce the desired extrudedshape. Although reference has been made to the extrusion of the powder mass, it is to be understood that it can be subjected to other types of hot working operations, such as rolling, forging or pressing, providing a suitable compact is initially produced. The hot working is preferably performed within the temperature range of 700 to 900 F.

Our invention is illustrated by the following examples wherein aluminum5.3% manganese5.1% copper (alloy A) and aluminum-5.6% manganese4.9% copper-0.2% chromium, 0.2% titanium-0.2% vanadium-0.2% zirconium (alloy B) atomized alloy powders were consolidated and the products hot worked. The powders were of a fineness such that over 70% passed through a 200 mesh screen and substantially all of the remainder passed through a 100 mesh screen. The alloy powders were placed in an extrusion press, heated to 800 F. and compressed under a pressure of 100,000 p.s.i. against a blind die. Following this compression, the blind die was removed and an extrusion die substituted therefor having an opening therein adapted to produce a rod in diameter. The compacted mass was extruded at a metal and press cylinder temperature of about 800 F. Tensile specimens were cut from the extruded rod and tested without any preliminary thermal treatment, some at room temperature and others at 600 F. after a 100-hour exposure at that temperature. The tensile properties of the hot worked product at room temperature and at 600 F. are given in Table 1 below:

4 TABLE 1 Tensile properties of extruded Al-Mn-Cu powder products sile and yield strength of the alloys exceeded those of the conventional Al-Cu-Mg-Mn composition referred to above. The addition of even small amounts of hardening elements increased the strength at 600 F. It is further noteworthy that the strength properties of bothalloys were attained without the benefit of any preliminary thermal treatment of the worked product, such as a solution heat treatment, which is an economic advantage.

This application is a continuation-in-part of our copending applicationSerial No. 724,227, filed March 27,

Having thus described our invention and certain embodiments thereof, we claim:

'1. A hot workedaluminum base alloy powder article free from aluminum oxide except as an incidental impurity and having a maximum iron content of 1%, said hot worked alloy, powder article being formed from atomized powder of an aluminum base alloy containing.

at least% byweight of aluminum, 2.5 to 12.5% by weight of manganeseand from 2.5 to 7.5% by weight of copper as the essential components, the amount of manganese always being in excess of the copper content,

' and the total amount of manganese and copper exceeding the total quantity of any hardening elements present in the alloy, said alloy being substantially free from elements which form a solid solution with aluminum other than copper, except as they occur as impurities, 7

said hot worked article being characterized in the asworked condition by a tensile strength at 600 F. after a hour exposure of not less than 10,000 p.s.i. and a yield strength of not less than 9,000 p.s.i.

2. A hot worked aluminum base alloy powder article according to claim 1 wherein the manganese content is 4 to 10 and the copper is 2.5 to 7.5.

3. A hot worked aluminum base alloy powder article according to claim 1 wherein the alloy also contains at least one hardening element selected from the group consisting of nickel, cobalt, chromium, titanium, vanadium, zirconium, tungsten, and molybdenum in amounts of 0.1 to 10% each, the total not exceeding 10% by weight, the total manganese and copper content of said alloy not being less than the amount of the hardening elements added thereto.

2,062,329 2,287,251 Jones June 23, 1942 2,809,891 Ennor Oct. 15, 1957 

1. A HOT WORKED ALUMINUM BASE ALLOY POWDER ARTICLE FREE FROM ALUMINUM OXIDE EXCEPT AS AN INCIDENTAL IMPURITY AND HAVING A MAXIMUM IRON CONTENT OF 1%, SAID HOT WORKED ALLOY POWDER ARTICLE BEING FORMED FROM ATOMAIZED POWDER OF AN ALUMINUM BASE ALLOY CONTAINING AT LEAST 70% BY WEIGHT OF ALUMINUM, 2.5 TO 12.5% BY WEIGHT OF MANGANESE AND FROM 2.5 TTO 7.5% BY WEIGHT OF COPPER AS THE ESSENTIAL COMPONENTS, THE AMOUNT OF MANGANESE ALWAYS BEING IN EXCESS OF THE COPPER CONTENT, AND THE TOTAL AMOUNT OF MAGANESE AND COPPER EXCEEDING THE TOTAL QUANTITY OF ANY HARDENING ELEMENTS PRESENT IN THE ALLOY, SAID ALLOY BEING SUBSTANTIALLY FREE FROM ELEMENTS WHICH FORM A SOLID SOLUTION WITH ALUMINUM OTHER THAN COPPER, EXCEPT AS THEY OCCUR AS IMPURITIES, SAID HOT WORKED ARTICLE BEING CHARACTERIZED IN THE ASWORKED CONDITION BY A TENSILE STRENGTH AT 600*F. AFTER A 100 HOUR EXPOSURE OF NOT LESS THAN 10,000 P.S.I. AND A YIELD STRENGTH OF NOT LESS THAN 9,000 P.S.I. 